Issue #13070: Fix a crash when a TextIOWrapper caught in a reference cycle

would be finalized after the reference to its underlying BufferedRWPair's
writer got cleared by the GC.

1 files changed, 15 insertions, 0 deletions

diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 608fc41..003a4f3 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -2338,6 +2338,21 @@ class CTextIOWrapperTest(TextIOWrapperTest):
         with self.open(support.TESTFN, "rb") as f:
             self.assertEqual(f.read(), b"456def")
 
+    def test_rwpair_cleared_before_textio(self):
+        # Issue 13070: TextIOWrapper's finalization would crash when called
+        # after the reference to the underlying BufferedRWPair's writer got
+        # cleared by the GC.
+        for i in range(1000):
+            b1 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
+            t1 = self.TextIOWrapper(b1, encoding="ascii")
+            b2 = self.BufferedRWPair(self.MockRawIO(), self.MockRawIO())
+            t2 = self.TextIOWrapper(b2, encoding="ascii")
+            # circular references
+            t1.buddy = t2
+            t2.buddy = t1
+        support.gc_collect()
+
+
 class PyTextIOWrapperTest(TextIOWrapperTest):
     pass